You can buy up to 18 Tonic slots altogether (there are 55 Tonics in total) in the Gatherer's Garden.
If a Tonic is buyable, I've taken its first appearance on the Gatherer's Garden list. In case of [presents] from the Sisters, there's the earliest level during which you can attain it. If a Tonic is received as a bonus for research, its localization has been marked as [research] and detailed info about it placed in the "Enemy research" chapter.
Reduces all physical damage.
[Armored Shell 2]
Further reduces physical damage taken.
You are able to salvage more ammunition from bodies and containers.
Drinking alcohol restores a small amount of EVE, rather than draining it.
The hacking needle moves slightly slower.
[Careful Hacker 2]
The hacking needle moves even slower.
Health Stations also refill your EVE.
Increases research damage bonuses.
Your hacked bots and turrets do more damage.
Little Sisters gather ADAM more quickly.
Dionysus Park [present]
Quiets your footsteps, and increases damage from melee attacks on unaware opponents, especially with the drill swing.
Increases damage dealt by the Drill.
[Drill Power 2]
Further increases damage dealt by the Drill.
Significantly decreases EVE cost of Plasmids, but limits weapon selection to the Drill, Hack Tool and Camera.
Gain health and eve when attacking with the drill.
Reduces electric damage received to zero and increases electrical damage done.
Causes the user to emit a burst of electricity when struck by a melee attack.
When you are damaged by elemental attacks, you gain a small amount of EVE.
You emit a random burst of fire, ice, or electricity when struck by melee attacks, damaging all around you.
Your Level 3 element streams siphon off health from your enemies.
Increases EVE Hypo carry capacity by 1.
First Aid Kits also give a small amount of EVE.
Reduces EVE consumption of all plasmids.
[EVE Saver 2]
Further reduces EVE consumption of all plasmids.
Increases the time you have when researching.
Gain a small increase in health from consumables.
Hacking success zones become a little larger.
Causes the user to emit a burst of fire when struck by a melee attack.
[Fountain of Youth]
Standing in water slowly restores HEALTH and EVE.
Increases the duration for which enemies are frozen, gives the Drill a chance to freeze the enemy upon impact.
Some health and EVE are gained after a successful hack.
[Hacker's Delight 2]
More health and EVE are gained after a successful hack.
Repair damaged bots and turrets with a small eve cost. Also gives random names to friendly bots and turrets.
Hacking a turret or bot raises its max health.
Your headshots do more damage.
Landing in a blue bonus zone completes a hack instantly.
You emit a burst of ice when struck by melee attacks, with a chance to freeze foes.
Increases the research score gained by damaging enemies.
[Keen Observer 2]
Further increases the research score gained by damaging enemies.
Deals more damage to turrets, cameras and bots.
Increases First Aid Kit carry capacity by 1.
Grants invisibility when standing still for a period of time.
Increases the amount of ADAM gained by 20 when accompanied little sister harvests a corpse. Amount of ADAM gained by harvesting a little sister remains unchanged.
Siren Alley [present]
Hacking has fewer stages.
Search corpses and containers a second time to get different loot.
Security Cameras and Turrets take two seconds longer to track the player.
Security is disabled for longer when hit with electricity.
[Short Circuit 2]
Security is disabled permanently when hit with electricity.
Reduces the length of hostile security alarms.
[Shorten Alarms 2]
Further reduces the length of hostile security alarms.
You move slightly faster.
Hacked vending prices are cheaper.
Provides a slight reduction to prices in vending machines.
[Vending Expert 2]
Provides a substantial reduction to prices in vending machines.
You take less damage from fire and inflict more damage when you use fire.