How to train baby to drink from glass/sippy cup

Hi mommies..hingi lang po ako ng advise kasi next year we will be returning to office na..my son who is 1 year and 2 mos is exclusively breastfed. Ayaw nya magmilk sa bottle at ayaw din nya mag drink ng milk sa baso/sippy cup kahit milk ko naman ang nakalagay. Naduduwal sya everytime na pinapainom namin sya..dede ko lang talaga ang gusto nya..any tips po? Thank you.