Capture a piece, take a drink. Similarly with warlight capture a bonus, take a drink.

Too few rules, perhaps something more like this:

You must have a beverage at all times, if empty, get another.
Beverage the amount of "fingers" of a piece's "value" each time you move and take pieces.
Upon promoting a pawn, the player that promoted it downs their beverage.
In the event of a stalemate or draw, use a boatrace to decide the winner.
If you win the game, your opponent owes you a beverage; if you lose you must buy the winner a beverage.

Think that's plenty of chess rules for now :)
Have fun!

Edited 9/25/2019 13:50:58

Drinking Chess was already invented
According to the creator the added rules are:
1. Drink once per turn
2. Never play with a catholic
3. First one to quit loses
4. Never play with a muslim
5. Wear 100% cotton shirt
6. The color black cannot be worn, as it symbolizes death
7. Any statements or deals made during the game cannot be used against speaker
8. Never play blindfolded
9. If you feel pressured, you can call it a draw
10. Ethnicities cannot drink their native drink
ex: Mexicans cannot drink tequila, Russians cannot drink vodka, French cannot drink shitty wine
11. Once 11 turns have passed, the King can teleport anywhere on the board
12. Spanish People can only play if they can prove they have no moorish ancestry
13. German people can only play if they can prove they are at least 90% of a combination Western or
Northern European
14. Certain ethnicities are not smart enough to play Drinking Chess, they cannot play as they would ruin
the game
15. Certain ethnicities cannot process alcohol as well, they cannot play as they would probably die
16. The Topic of Eugenics shall not be brought up
17. If the topic of Eugenics is brought up, all pawns will be wiped off the board
18. If player doesn't feel good, they must keep playing or suffer consequences of embarrassment
19. People are not allowed under the table
20. The move Earthquake is valid, this involves shaking the board and continue playing with the new
positions
21. You must be sane to legally play