1. Have "damaged" canteen in possession.
2. Found "pristine" canteen.
Canteen in possession = 100% filled
Found Canteen = 59% filled
3. Take pristine canteen into hands and drink all.
4. Animation appears to be finished take 100% filled damaged canteen in possession and fill pristine canteen in hands. Damaged canteen now registers 0% filled.
5. Take pristine canteen in hands and swap it out for damaged one in possession.
6. The new pristine canteen now in your possession registers 59% filled.
7. Drop the damaged canteen.