Trying to maintain a routine of exercise when you are on holidays, and really have no routine as such, in your day, can be quite difficult. My suggestion is to look at the activities you have planned for each day and see if any of those can be included as exercise or physical activity. You may be intending on trekking 12 km, or skiing all day. These can be classed as physical activity. Sitting around, relaxing pool-side, is not classified as physical activity.
If you have non-active days, try to go for a walk or participate in an exercise routine before your day begins. If the place you are staying at has a gym, then use their facilities. If not, take some resistance bands on holidays with you. These are such versatile pieces of exercise equipment. They don’t weigh much and don’t take up much space in your luggage.
If you are unsure what exercises to do, check out my exercise videos that include resistance bands.