The second drink was 2/12=1/6 the size of the first drink
So it had 1/6*3=1/2 the caffeine
That means it had 1/2*250=<<250/2=125>>125 grams of caffeine
So the total amount of caffeine he drank was 125+250=<<125+250=375>>375 grams
So he consumed 375*2=<<375*2=750>>750 grams of caffeine for the day
#### 750