To quickly build abdominal muscles, you can try the following exercises:

1. Planks: Hold a plank position for as long as you can, focusing on engaging your core muscles.

2. Crunches: Perform crunches to target the upper abdominal muscles. Make sure to keep your lower back pressed into the floor.

3. Leg raises: Lie on your back and lift your legs towards the ceiling, engaging your lower abdominal muscles.

4. Russian twists: Sit on the floor with your knees bent and twist your torso from side to side, engaging your oblique muscles.

5. Bicycle crunches: Lie on your back and mimic a pedaling motion while bringing your elbow to the opposite knee.

Consistency and proper form are key to seeing results quickly. Additionally, incorporating cardiovascular exercise and intaining a healthy t can help reveal your abdominal muscles.