Check the Case’s LED
Though it is not very precise, you can use your AirPods case to estimate how much juice you have remaining. Depending on your case, there is a button on the case that you use to pair your AirPods initially to your device. You can use this same button to check your battery level.
Press the button and look at the LED indicator light on the case. If it is green, then the case or the earbuds have ample battery life. The battery is drained and must be charged if the light is red. This trick works for the case and the earbuds. If your earbuds are in the case, then the indicator reflects the battery life of the AirPods in the case. If the case is empty, then the color shows the power status of the case.