Atmospheric escape plays a fundamental role in shaping the properties of exoplanets. The metastable near-infrared (nIR) helium triplet at 1083.3 nm ( He I ) is a powerful proxy of extended and evaporating atmospheres. We used the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo to search for absorption in the upper atmospheres of five close-in giant planets hosted by the K and M dwarf stars of our sample, namely WASP-69\,b, WASP-107\,b, HAT-P-11\,b, GJ\,436\,b, and GJ\,3470\,b. We focused our analysis on the nIR triplet, performing high-resolution transmission spectroscopy by comparing the in-transit and out-of-transit observations. In instances where nightly variability in the absorption signal was identified, we investigated the potential influence of stellar magnetic activity on the planetary absorption signal by searching for variations in the Halpha transmission spectrum. We spectrally resolve the triplet and confirm the published detections for WASP-69\,b (3.91pm 0.22<!PCT!>, 17.6sigma ), WASP-107\,b $<!PCT!>, 10.5sigma ), HAT-P-11\,b (1.36pm 0.17<!PCT!>, 8.0sigma ), and GJ\,3470\,b $<!PCT!>, 4.7sigma ). We do not find evidence of extra absorption for GJ\,436\,b. We observe night-to-night variations in the absorption signal for WASP-69\,b, associated with variability in Halpha , which likely indicates the influence of pseudo-signals related to stellar activity. Additionally, we find that the signal of GJ\,3470\,b originates from a single transit observation, thereby corroborating the discrepancies found in the existing literature. An inspection of the Halpha line reveals an absorption signal during the same transit event. By combining our findings with previous analyses of GIANO-B measurements of planets orbiting K dwarfs, we explore potential trends with planetary and stellar parameters that are thought to affect the absorption of metastable He I . Our analysis is unable to identify clear patterns, thus emphasising the necessity for additional measurements and the exploration of potential additional parameters that may be important in controlling absorption in planetary upper atmospheres.