Lemon juice and Vinegar.

Using  lemon juice or vinegar can cause problems when cleaning windows. But probably not if you only use them  occasionally. Lemon juice despite being so sour is fill of sugar. Which attracts insects that walk over your clean windows looking for sugar to eat and leave behind droppings. In the worst case lemon juice will attract ants which can chew out your wooden window frames in search if the sugar.

Vinegar also contains sugar however not in the same quantity as lemon juice. Vinegar tends not to attract insects like lemon juice however it causes other problems. Such as regularly coating raw wooden window frames in vinegar will start to dissolve the wood and leach out the natural oils. Over time vinegar will make paint or varnish on the wooden window frames porous and chalky causing the frames to need  repainting or varnishing in half the usual time or less. Vinegar on aluminium window frames will reduce the life of the finish and eventually eat right through the aluminium.

At the risk of repeating my self. If you only use lemon juice or vinegar occasionally you probably wont have any major problems.

Read why Modern inks are not good for the window cleaning process